I'm probably doing it wrong. The attached file is an example of what I'm trying.
dethead.sh

After entering project details I get the following pop up. Depending on y/n I end up in a detached head state.

Copying from template version 1.0.4
    create  .copier-answers.yml
    create  .github
    create  .github/copilot-instructions.md
 identical  .git
  conflict  .git/index
?  Overwrite .git/index? (Y/n)

You define the _exclude setting which overrides its default values that include the .git directory. See the info admonition in the docs. You have two options:

1. Add at least the .git directory to your _exclude list.
2. Move the template files/directories in a subdirectory (e.g., template) and define the _subdirectory setting accordingly (e.g., _subdirectory: template).

I generally recommend option 2 because it separates template files/directories from project files/directories of the template (e.g., the project may have a README file to document the Copier template and the template may have a README file to document the generated project).